Organosilicon endcapper having one silicon-bonded hydrogen atom

ABSTRACT

An organosilicon compound comprising one silicon-bonded hydrogen atom described by formula                    
     or by formula                    
     where each R 1  and R 1′  is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each R 2  is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each X and X′ is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo; t is 2 or 3; n is 0, 1, or 2; and each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments. The organosilicon compounds comprising one silicon-bonded hydrogen atom of the present invention are useful as endcappers for polymers.

This is a continuation-in-part of application number 09/218,534 filed on Dec. 21, 1998, now abandoned.

FIELD OF THE INVENTION

An organosilicon compound comprising one silicon-bonded hydrogen atom described by formula

or by formula

where each R¹ and R^(1′) is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each R² is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each X and X′ is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo; t is 2 or 3; n is 0, 1, or 2; and each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments.

BACKGROUND OF THE INVENTION

Polyorganosiloxane compositions which cure to elastomeric materials at room temperature are well known. Such compositions can be obtained by mixing polydiorganosiloxanes having reactive or hydrolyzable groups, such as silanol or alkoxy groups, with silane crosslinking agents, for example, alkoxysilanes, acetoxysilanes, oximosilanes, or aminosilanes, and catalysts as needed. Generally, the polydiorganosiloxanes may have 1 to 3 reactive groups per chain end. Compositions comprising these ingredients can then be cured by exposure to atmospheric moisture at room temperature.

The cure rate of a particular composition is dependent on a number of factors including the type of reactive or hydrolyzable group utilized. It is known that different hydrolyzable groups have different reactivities and even the same type of hydrolyzable group can have different reactivities. For example, in the presence of moisture, a silicon-bonded acetoxy group will hydrolyze more rapidly than a silicon-bonded alkoxy group. In addition if, for example, a silicon-bonded trialkoxy group is present on a polymer, it is believed that each silicon-bonded alkoxy group has a different reactivity, with the alkoxy group first reacted being “most reactive.” Generally, once the first alkoxy group on a silicon atom reacts it takes a longer time for the second alkoxy group on the same silicon atom to react, and even longer for the third. Therefore, it would be desirable to prepare an organosilicon compound which can endcap a polymer and be capable of providing more than one “most” reactive hydrolyzable group per polymer chain end.

The objective of the present invention is to prepare an organosilicon compound comprising one silicon-bonded hydrogen atom which is capable of endcapping a polymer and providing more than one “most” reactive hydrolyzable group per polymer chain end.

SUMMARY OF THE INVENTION

The present invention is an organosilicon compound comprising one silicon-bonded hydrogen atom described by formula

or by formula

where each R¹ and R^(1′) is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each R² is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each X and X′ is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo; t is 2 or 3; n is 0, 1, or 2; and each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an organosilicon compound comprising one silicon-bonded hydrogen atom described by formula

or by formula

where each R¹ and R^(1′) is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each R² is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each X and X′ is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo; t is 2 or 3; n is 0, 1, or 2; and each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments described by formula

where R² is as defined above; each G is an independently selected divalent hydrocarbon radical free of aliphatic unsaturation comprising about 2 to 18 carbon atoms; and c is a whole number from 1 to about 6.

In formula (1), each R¹ is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms. The hydrocarbon radicals free from aliphatic unsaturation represented by R¹ may be substituted or unsubstituted. Examples of hydrocarbon radicals free from aliphatic unsaturation include alkyl radicals, aryl radicals, and aralkyl radicals. Examples of alkyl radicals include methyl, ethyl, hexyl, octadecyl, cyclobutyl, cyclopentyl, cyclohexyl, 3,3,3-trifluoropropyl, chloromethyl, and chlorocyclopentyl. Examples of aryl radicals include phenyl, tolyl, xylyl, 2,4-dichlorophenyl, and tetrachlorophenyl. Examples of aralkyl radicals include benzyl, beta-phenylethyl, gamma-tolylpropyl, para-chlorobenzyl, and 2-(bromophenyl)propyl. Preferably, each R¹ is selected from the group consisting of alkyl radicals comprising 1 to about 8 carbon atoms and aryl radicals comprising about 6 to 8 carbon atoms. More preferably, R¹ is an alkyl radical comprising 1 to about 8 carbon atoms. Most preferably, R¹ is n-propyl.

In formula (IA), each R^(1′) is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms. The hydrocarbon radicals free from aliphatic unsaturation represented by R^(1′) may be substituted or unsubstituted. Examples of hydrocarbon radicals free from aliphatic unsaturation include alkyl radicals, aryl radicals, and aralkyl radicals. Examples of R^(1′) are as described above for R¹. Preferably, each R^(1′) is selected from the group consisting of alkyl radicals comprising 1 to about 8 carbon atoms and aryl radicals comprising about 6 to 8 carbon atoms. More preferably, R^(1′) is an alkyl radical comprising 1 to about 8 carbon atoms. Most preferably, R^(1′) is methyl.

In formulas (1) and (IA), each R² is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms. The hydrocarbon radicals free from aliphatic unsaturation represented by R² may be substituted or unsubstituted. Examples of hydrocarbon radicals free from aliphatic unsaturation include alkyl radicals, aryl radicals, and aralkyl radicals. Examples of R² are as described above for R¹. Preferably each R² is an independently selected alkyl radical. More preferably each R² is an independently selected alkyl radical comprising 1 to about 8 carbon atoms. Most preferably each R² is methyl.

In formula (1), each X is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo. The halogen atoms can be chlorine, bromine, fluorine, and iodine. Examples of alkoxy groups include methoxy, ethoxy, iso-propoxy, butoxy, cyclohexoxy, phenoxy, 2-chloroethoxy, 3,3,3-trifluoropropoxy, 2-methoxyethoxy, and p-methoxyphenoxy. Examples of acyloxy groups include acetoxy, propionoxy, benzoyloxy, and cyclohexoyloxy. Examples of ketoximo groups include dimethylketoximo, methylethylketoximo, methylpropylketoximo, methylbutylketoximo, and diethylketoximo. Preferably each X is independently selected from the group consisting of alkoxy, acyloxy, and ketoximo. More preferably each X is independently selected from the group consisting of alkoxy and acyloxy, with each X being an independently selected alkoxy group being most preferred.

In formula (1), each X′ is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo. Examples of X′ are as described above for X. Preferably each X′ is independently selected from the group consisting of alkoxy, acyloxy, and ketoximo. More preferably each X′ is independently selected from the group consisting of alkoxy and acyloxy, with each X′ being an independently selected alkoxy group being most preferred.

In formulas (1) and (IA), subscript t is 2 or 3 and is preferably 2.

In formulas (1) and (IA), subscript n is 0, 1, or 2 and is preferably 0 or 1.

In formulas (I) and (IA), each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments described by formula

where R² is as defined above; each G is an independently selected divalent hydrocarbon radical free of aliphatic unsaturation comprising about 2 to 18 carbon atoms; and c is a whole number from 1 to about 6.

Examples of the divalent hydrocarbon radicals free of aliphatic unsaturation represented by Z and G include alkylene radicals, arylene radicals and aralkylene radicals. The divalent hydrocarbon radicals represented by Z and G may be substituted or unsubstituted. Examples of alkylene radicals include ethylene, methylmethylene, propylene, butylene, pentylene, hexylene, cyclopentylene, cyclohexylene, chloroethylene, and chlorocyclopentylene. Examples of arylene radicals include phenylene, tolylene, xylylene, 2,4-dichlorophenylene, and tetrachlorophenylene. Examples of aralkylene radicals include benzylene, beta-phenylethylene, gamma-tolylpropylene, para-chlorobenzylene, and 2(bromophenyl)propylene. When Z is a combination of divalent hydrocarbon radicals and siloxane segments as described above, each G is preferably an independently selected alkylene radical, and each G is more preferably an independently selected alkylene radical comprising about 2 to 8 carbon atoms. Preferably, each Z is an independently selected divalent hydrocarbon radical free from aliphatic unsaturation. It is more preferred for each Z to be an independently selected alkylene radical, with an independently selected alkylene radical comprising about 2 to 8 carbon atoms being most preferred for each Z.

The organosilicon compound comprising one silicon-bonded hydrogen atom described by formula (I) may be prepared by mixing an organohydrogensiloxane described by formula

 R¹ _(4-(t+1))Si-(O-SiR² ₂H)_(t+1,)  (II)

with an organosilicon compound containing one aliphatic unsaturation described by formula

Y-SiR² _(n)X_(3-n)  (III)

The organosilicon compound comprising one silicon-bonded hydrogen atom described by formula (IA) may be prepared in a similar manner by mixing an organohydrogensiloxane described by formula

with an organosilicon compound containing one aliphatic unsaturation described by formula

Y-SiR² _(n)X′_(3-n)  (IIIA),

in each case in the presence of a hydrosilylation catalyst, where R¹, R^(1′), R², X, X′, t, and n are as defined above, and Y is selected from the group consisting of hydrocarbon radicals comprising one aliphatic unsaturation and 2 to about 18 carbon atoms and a combination comprising one aliphatic unsaturation of hydrocarbon radicals, siloxane segments, and a divalent hydrocarbon radical free of aliphatic unsaturation comprising about 2 to 18 carbon atoms described by formula

where R², G, and c are as defined above and M is an independently selected hydrocarbon radical comprising one aliphatic unsaturation and 2 to about 18 carbon atoms.

The hydrocarbon radicals represented by Y and M may be substituted or unsubstituted. Examples of the hydrocarbon radicals comprising one aliphatic unsaturation represented by Y and M include alkenyl radicals such as vinyl, allyl, butenyl, hexenyl, and octenyl, and cycloalkenyl radicals such as cyclopentenyl, cyclohexenyl, and chlorocyclopentenyl. With non-cyclic compounds comprising one aliphatic unsaturation, it is preferred for the aliphatic unsaturation to be at the terminal end of the hydrocarbon radical attached to silicon, for example as in 1-butenyl, i.e. H₂C═CHCH₂CH₂—.

When Y is a combination comprising one aliphatic unsaturation of hydrocarbon radicals and siloxane segments as described above, it is preferred that G be an alkylene radical and M an alkenyl radical, and more preferable that G be an alkylene radical comprising about 2 to 8 carbon atoms and M an alkenyl radical comprising 2 to about 8 carbon atoms. Preferably, Y is a hydrocarbon radical comprising one aliphatic unsaturation. It is more preferred for Y to be an alkenyl radical, with an alkenyl radical comprising 2 to about 8 carbon atoms being most preferred for Y.

The organohydrogensiloxanes described by formula (II) may be prepared by known methods such as taught in U.S. Pat. No. 5,446,185 which is hereby incorporated by reference and are commercially available. The organohydrogensiloxanes described by formula (IA) may also be prepared by known methods. The organosilicon compounds containing one aliphatic unsaturation described by formulas (III) and (IIIA) may also be prepared by known methods and are commercially available.

Catalysts typically employed for hydrosilylation reactions, such as platinum group metal-containing catalysts are used as catalysts for the reaction between the organohydrogensiloxane described by formula (II) or (IIA) and the organosilicon compound containing one aliphatic unsaturation described by formula (III) or (IIIA), respectively. By “platinum group metal” it is meant ruthenium, rhodium, palladium, osmium, iridium, and platinum. Platinum group metal-containing catalysts particularly useful in the present composition are the platinum complexes prepared as described by Willing, U.S. Pat. No. 3,419,593, and Brown et al, U.S. Pat. No. 5,175,325, each of which is hereby incorporated by reference to show such complexes and their preparation. Preferred catalysts are complexes of platinum with vinylsiloxane. Other examples of useful platinum group metal-containing catalysts can be found in Lee et al., U.S. Pat. No. 3,989,668; Chang et al., U.S. Pat. No. 5,036,117; Ashby, U.S. Pat. No. 3,159,601; Lamoreaux, U.S. Pat. No. 3,220,972; Chalk et al., U.S. Pat. No. 3,296,291; Modic, U.S. Pat. No. 3,516,946; Karstedt, U.S. Pat. No. 3,814,730; and Chandra et al., U.S. Pat. No. 3,928,629 all of which are hereby incorporated by reference to show useful platinum group metal-containing catalysts and methods for their preparation.

The amount of catalyst useful in effecting the hydrosilylation reaction to make the composition of the present invention is not narrowly limited as long as there is a sufficient amount present to accelerate a reaction between the hydrosilyl groups and the groups comprising an aliphatic unsaturation. The appropriate amount of the catalyst will depend upon the particular catalyst used. In general as low as about 0.1 part by weight of platinum group metal based on 1 million parts by weight of total reactants may be useful (ie. 0.1 ppm). Preferably the amount of platinum group metal is from about 1 to 60 ppm. More preferred is from about 10 to 40 ppm platinum group metal.

The platinum group metal-containing catalyst may be added as a single species or as a mixture of two or more different species. Adding the catalyst as a single species is preferred.

The temperature of the hydrosilylation reaction is not strictly specified, but usually falls within the range of about 20° to 150° C. and preferably within the range of about 300 to 110° C.

The molar ratio of aliphatic unsaturated groups to hydrosilyl groups useful in the present invention will vary depending upon the individual compositions. However, to ensure the highest yield of the organosilicon compound comprising one silicon-bonded hydrogen atom, the molar ratio of aliphatic unsaturated groups to hydrosilyl groups should be t/t+1:1, where t is as defined above.

After completion of the hydrosilylation reaction, the organosilicon compound comprising one silicon-bonded hydrogen atom described by formulas (I) and (IA) may be recovered by standard methods for separating liquid mixtures, such as by distillation from the reaction mixture under reduced pressure, recrystallization, or solvent fractionation. As persons skilled in the art will understand, the distilled reaction mixture containing the organosilicon compound comprising one silicon-bonded hydrogen atom described by formula (IA) may also contain isomers of this compound depending on which specific hydrogen atoms react.

More preferred compounds of the invention are

and

where Propyl is n-propyl and Me is methyl , with the latter compound being most preferred. The method of preparing the latter compound is also preferred because a larger, improved yield of the adduct containing one silicon-bonded hydrogen atom is obtained. Although not wanting to be bound by any one theory, the inventors believe this unexpected improvement in yield is due to the increased selectivity of the terminal hydrosilyl groups over the pendant hydrosilyl group during the hydrosilylation reaction.

The organosilicon compounds comprising one silicon-bonded hydrogen atom of the present invention are useful for endcapping polymers, and as adhesion promoters and crosslinkers. Polymers endcapped with the organosilicon compounds of the present invention ran be used for preparing sealants, adhesives, and coatings. Persons skilled in the art will also understand that the organosilicon compounds of the present invention in addition to endcapping polymers may also be found pendant on the polymer chain.

This invention is further illustrated by the following examples which are presented for that purpose and are not intended to limit the scope of the claims herein. As used in the examples, Me is methyl and Propyl is n-propyl. The gas liquid chromatograph used to analyze each composition was a Hewlett Packard 5890 Series II with a flame ionization detector.

EXAMPLE 1

203 g (0.686 mol) Tris(dimethylsiloxy)-n-propylsilane prepared as described in U.S. Pat. No. 5,446,185 and 1.8 g of a solution of a platinum vinylsiloxane complex containing 31 ppm platinum metal were heated to 100° C. The heat was then removed and 150 g (1.01 mol) of vinyltrimethoxysilane were added dropwise over a period of about 45 min. with sufficient stirring to maintain a pot temperature of approximately 103-105° C. Analysis of the reaction mixture by gas liquid chromatography showed a yield of approximately 40% of an organosilicon compound comprising one silicon-bonded hydrogen atom. The reaction mixture was distilled to yield 141 g of the organosilicon compound having the following formula and boiling at 155° C. under 0.5 mm Hg pressure.

EXAMPLE 2

(A) A mixture consisting of a 2:1 molar ratio of HMe₂SiCl and HMeSiCl₂ was added dropwise to a 5 fold molar excess of water (based on total SiCl bonds) which was stirred and held at approximately 10-151° C. by means of a recirculating cooling bath. After the addition was complete, the mixture was stirred for 15 minutes, and then separated. The organic phase was washed 3 times with 1% NaHCO₃ solution (roughly equal volumes to the organic phase each time) and 3 volumes of distilled water. The organic layer was then dried over MgSO₄ overnight and then filtered. Analysis of the reaction mixture by gas liquid chromatography showed a yield of approximately 30% of 1,1,3,5,5-pentamethyltrisiloxane. The reaction mixture was distilled to separate out the 1,1,3,5,5-pentamethyltrisiloxane having the following formula and boiling at 118° C. at atmospheric pressure.

(B) 38.8 g (0.2 mol) 1,1,3,5,5-pentamethyltrisiloxane prepared as described above in (A) and 0.30 g of a platinum vinylsiloxane complex containing 20 ppm platinum metal were heated to 90° C. The heat was then removed and 59.2 g (0.4 mol) of vinyltrimethoxysilane was added dropwise over a period of 20 minutes with sufficient stirring to maintain a pot temperature of approximately 90-100° C. Analysis of the reaction mixture by gas chromatography showed a yield of approximately 63% of organosilicon compounds comprising one silicon-bonded hydrogen atom. Distillation of the reaction mixture yielded 53 g of organosilicon compounds comprising one silicon-bonded hydrogen atom boiling at 151° C. under 4.4 mm Hg pressure and primarily comprising an organosilicon compound having the following formula:

however, a small amount of an isomer having the following formula

was also present. 

We claim:
 1. An organosilicon compound comprising one silicon-bonded hydrogen atom described by formula

where each R¹ is an independently selected unsubstituted hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each R² is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each X is independently selected from the group consisting of halogen, alkoxy, and ketoximo; t is 2 or 3; n is 0, 1, or 2; and each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments described by formula

where R² is as defined above; each G is an independently selected divalent hydrocarbon radical free of aliphatic unsaturation comprising about 2 to 18 carbon atoms; and c is a whole number from 1 to about
 6. 2. The organosilicon compound of claim 1, where each Z is an independently selected divalent hydrocarbon radical free of aliphatic unsaturation.
 3. The organosilicon compound of claim 1, where each Z is an independently selected alkylene radical.
 4. The organosilicon compound of claim 1, where each Z is an independently selected alkylene radical comprising about 2 to 8 carbon atoms.
 5. The organosilicon compound of claim 2, where each X is independently selected from the group consisting of alkoxy and ketoximo.
 6. The organosilicon compound of claim 1, where each X is an independently selected alkoxy group.
 7. The organosilicon compound of claim 2, where each X is an independently selected alkoxy group.
 8. The organosilicon compound of claim 4, where each X is an independently selected alkoxy group.
 9. The organosilicon compound of claim 8, where t is
 2. 10. The organosilicon compound of claim 9, where n is 0 or
 1. 11. The organosilicon compound of claim 8, where n is 0, each R¹ is an independently selected unsubstituted alkyl radical comprising 1 to about 8 carbon atoms, and each R² is an independently selected alkyl radical comprising 1 to about 8 carbon atoms.
 12. An organosilicon compound comprising one silicon-bonded hydrogen atom described by formula

where each R¹′ is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising 1 to about 18 carbon atoms; each R² is an independently selected hydrocarbon radical free from aliphatic unsaturation comprising I to about 18 carbon atoms; each X′ is independently selected from the group consisting of halogen, alkoxy, acyloxy, and ketoximo; t is 2 or 3; n is 0, 1, or 2; and each Z is independently selected from the group consisting of divalent hydrocarbon radicals free of aliphatic unsaturation comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments described by formula

where R² is as defined above; each G is an independently selected divalent hydrocarbon radical free of aliphatic unsaturation comprising about 2 to 18 carbon atoms; and c is a whole number from 1 to about
 6. 13. The organosilicon compound of claim 12, where each Z is an independently selected divalent hydrocarbon radical free of aliphatic unsaturation.
 14. The organosilicon compound of claim 12, where each Z is an independently selected alkylene radical.
 15. The organosilicon compound of claim 12, where each Z is an independently selected alkylene radical comprising about 2 to 8 carbon atoms.
 16. The organosilicon compound of claim 13, where each X′ is independently selected from the group consisting of alkoxy, acyloxy, and ketoximo.
 17. The organosilicon compound of claim 14, where each X′ is independently selected from the group consisting of alkoxy and acyloxy.
 18. The organosilicon compound of claim 12, where each X′ is an independently selected alkoxy group.
 19. The organosilicon compound of claim 15, where each X′ is an independently selected alkoxy group.
 20. The organosilicon compound of claim 18, where t is
 2. 21. The organosilicon compound of claim 19, where t is
 2. 22. The organosilicon compound of claim 20, where n is 0 or
 1. 23. The organosilicon compound of claim 21 where n is 0 and each R^(1′) and R² is an independently selected alkyl radical comprising 1 to about 8 carbon atoms.
 24. An organosilicon compound comprising one silicon-bonded hydrogen atom described by formula

or by formula 